1. Field of the Invention
Apparatuses, methods, and systems consistent with the present invention relate to a wireless communication which operates in a multiple-input multiple-output (MIMO) mode.
2. Description of the Related Art
Signal transmission using a multiple-input multiple-output (MIMO) mode is a high speed wireless communication technology. The MIMO mode is literally based on input/output of a signal using a plurality of antennas. A plurality of transmission data can be simultaneously transmitted at the same time and in the same frequency band using the plurality of antennas in the MIMO mode. When the number of simultaneously transmittable channels increases, wire traffic per unit time also increases by an amount corresponding to the increase in the number of transmittable channels. Accordingly, communication speed can be substantially increased. Also, in the MIMO mode, a frequency band does not increase even when the communication speed increases.
However, since a plurality of modulated signals having a carrier component of the same frequency is simultaneously transmitted, a receiver uses an apparatus for separating modulated signals that interfere with each other. In the MIMO mode, modulated signals are separated using a channel matrix indicating the transmission characteristics of a wireless transmission path. The channel matrix can be detected using, for example, a method of assuming a channel using a pilot symbol, or the like.
However, each signal modulated during transmission may not be reproduced with a high degree of precision in some channel matrices due to noise, etc. Accordingly, several technical improvements to MIMO signal detection are being studied, and various methods of separating signals are being disclosed. For example, in W. Wang, P. Gong, K. Niu, W. Wu, J. Zhang, M. Weckerle, “Decision Feedback Aided Detection Based on Lattice Reduction in MIMO Systems”, VTC2006-Spring, Melbourne, May 2006 (hereinafter “Wang et al.”), a method of separating modulated signals using a channel matrix obtained by lattice basis reduction is disclosed.
However, using a MIMO signal detection technology disclosed in Wang et al., the likelihood of an estimated modulated signal cannot be calculated at each bit illustrated by the estimated modulated signal.